Jump to content

Throttle bodies


Recommended Posts

Posted

could somebody(s) please explain in simplish terms what throttle bodies are and why if they are fitted  you have more power, i am looking at buying a westie very soon, originally(b4 joining this site) i didnt know that injection systems gave more power than carbs  :durr: i honestly dont know if i will be able to afford an injected 16valver it may be a carbed version (although i will be very happy with that) but it is nice to know the difference just in case , TIA  ;)

Posted

Injection doesn't give more power than carbs...........it improves drivability and fuel consumption, and the extra effeciency *might* liberate some extra horsepower, but that isn't guaranteed.

Posted
Injection doesn't give more power than carbs...........

*cough*

Check your power curves....  :p  :D  :D

Actually, to be fair, it does to a large extent depend on the type of fuel injection set up being used.

Standard injection systems on cars are a compromise between fuel economy, emissions, cost and power outputs.

But as soon as you decide you want more power then the standard injection has to go because it's not up to the job of delivering enough air and fuel to reap big power outputs.

Throttle bodies, in very simple terms, fall into 2 main categories :

- the twin choke weberesque variety (they look like a pair of carbs); and

- individual throttle bodies

The difference between one throttle body and another is the way it flows air and the way it mixes that air with the fuel you're delivering.  Individual tapered throttle bodies do have clear advantages in terms of the way they deliver mid range torque (and hence power) although at wide open throttle they're unlikely to be *that* different to the twin choke variety.

Carbs on the other hand have to work on a series of compromises.  The chances of you being able to deliver exactly the right amount of fuel at the right throttle opening are lower because of the way they work - you can't open / close the jets for specific durations in the same way you can with fuel injectors.  That's not to say they can't produce good results, just that, as Blatman says, there's a compromise in terms of driveability and fuel economy vs. fuel injection.

Posted

wrightster

Put simply

Throttle bodies i.e. Injection will produce the same peak power as Carbs.

Twin choke bodies will produce more torque in the mid-range than carbs  

Individual tapered throttle bodies will be better again in the mid-range (marginally).

This is I think due to their ability to give the engine exactly what it needs when it needs is i.e. fuel to air mixture.

This will also give better fuel economy (with injection)

Was that simple :durr:

Andy :zzz:

This all ignores the standard injection systems found on prouction engines & is only based on Throttle bodies.

I take no responisbility for anything i ever say EVER :p  :D  :D  :D  :arse:  :xmas:  :blush:  :sheep:  :zzz:

Posted
I take no responisbility for anything i ever say EVER

Good job really !!   :p  :D  :D

I'd still take issue with the fact that carbs produce the same amount of peak power as throttle bodies.  I just don't think, in practice, they're sufficiently accurate to deliver the right fuel / air mixture.

For example, accepted wisdom is that if you bolt a pair of Weber 45s onto a standard 2.0 VX you'll get in the region of 180bhp. With a pair of 48s might see a little more.  But bolt on a tapered throbble botty kit and you can expect to see around 205bhp, with no other mods.

Now the difference has to be coming from somewhere, and I'd venture to suggest, along with the improved inlet manifold design, it's in the way the throbble botties flow air and the way in which you can accurately meter the fuel flow and ignition.

Not trying to pick an argument here or anything like that, just my offering my thoughts on the subject.

Posted

Ding to what Nick said! (I do like that saying Nick...)

A pair of 45mm throttle bodies in theory should make more power all through the range (top end included) than equivelent sized Webers/Dellortos. Throttle bodies do not have a venturi to retrict the intake system.

The difference *could* be offset by fitting yet bigger carbs, but then midrange/driveabilty would be sacrificed. I dont honestly know it would compare, but I would guess that 40mm throttle bodies would give virtually the same max bhp reading as 45mm carbs, but give a s***load (techinical term) more power in the midrange.  

But ultimately, its not the peak power that counts, because in reality, how long does the car spend at this point? To sacrifice a couple of bhp at peak to say a 10 bhp gain in the midrange is well worth it IMO.....

If you can stretch to it, throttle bodies have got to be the way to go.

HTH Stu.

Posted
For example, accepted wisdom is that if you bolt a pair of Weber 45s onto a standard 2.0 VX you'll get in the region of 180bhp. With a pair of 48s might see a little more.  But bolt on a tapered throbble botty kit and you can expect to see around 205bhp, with no other mods.

In my experience, you're wrong, and I'll qualify that. I'm sure that you're aware that my green car, and Gee Fins carbon car are "sister cars", from the same builder, with comparable (identical) engine and drive train components (before the sequential 'box was added to Gee's car). On the rollers, they made the same power to within about 1 or 2bhp, and similar torque across the range. The only difference in the engines, AFAIK, is mine has Jenvey "DCOE" type throbble botties, and Gee's is 3D mapped on 45's..............I'll need to just double check the actual numbers, but I'm pretty sure Nick was at Emerald when the carbon car made 180something bhp, which is what mine makes. The difference is small enough to make the conversion from Gee's carbs to my TB's questionable, in terms of the statement that "adding throbble botties makes more power". It would, in this case, be an expensive conversion for only a couple of horsepower at best, and I don't believe that enough torque would be liberated that you could feel a diffefrence from the drivers seat.

Your mileage may vary, but this is what I have experience of. I need to get my car on the rollers at Dave Walkers, I guess, for some empirical data collection (unless Gee has a copy of the torque/power curve we could look at.......). Is there a Se7ens net day in the offing soon?

All that notwithstanding, if you can afford to fit throbble botties, then do so. It's a no brainer........

Posted
But bolt on a tapered throbble botty kit and you can expect to see around 205bhp, with no other mods.

Are you sure, sounds like extreemly cheap HP????

Where does this info come from, an extra 15bhp just by fitting throttle bodies!!!!

I think that a properly mapped 3D system on carbs will give good HP similar to trobbel botties????

Andy :t-up:

Not trying to pick an argument

Too late pal, where do you live?  :p  :D  :D  :D

Posted

I know of a well respected dyno operator and engine tuner that found disappointing results from a Vx on Tapered throttle bodies the engine should have made a claimed 208bhp. The said engine made 175bhp the car went back to the supplier of said throttle bodies where some excuses had been made for the lower than claimed Bhp the car went back to the same rolling road after work had been done on the car and it made 180ish Bhp. I am not knocking the tapered throttle bodies quite the opposite as I have them fitted to by car but I think that they are only marginally (if that) better than normal throttle bodies. I can say that they are better than carbs though as I have done more or less back to back test on this and I had a hole in the torque curve at 5000rpm on carbs. When I fitted t/bodies the torque curve was much better. I then went on to play with the tuned lengths on the induction which produced more mid range power. That said I could have sorted the tuned lengths on the carbs but the torque curve would not be as good as it is on t/bodies. The torque curve is almost completely flat from 4000-7000rmp peaking at 171lbft torque. This is not massive power I know but if I choose to go for more power then the t/bodies are a must as the driveability would be lost on carbs and a 250bhp engine. :cool:

Posted

Thanks to all of you for your help on that one  :D  :D

Posted

Blatman - To clarify, I was actually making a comparison between carbs and *tapered* throttle body set ups to point out the improvements in mid range torque and peak power.

The inlet manifold which is used for the DCOE type throttle bodies is compromised because it has to turn the fuel / air mixture through at least 30 degrees, which isn't good for the flow.  The tapered kit has a far smoother flow into the cylinder and my understanding was that the taper helped to increase airflow and hence allowed more air and fuel to be mixed at any given point.

Two Dinners - I think I know which engine tuner you're referring to and all I can say is that engines will vary.  Not always a logical reason why, but they do.  My kit is producing exactly what it says on the tin and I don't claim to have done anything special to achieve that, other than spending a fair bit of time matching up the throttle bodies to the inlet manifold and the manifold to the head.

Incidentally, windy and a good few others used the 208bhp kit on their engines and, unless I'm very much mistaken, their engines all produced the qouted power outputs.

Bananaman - Phoenix, Arizona !  Bring it on !!  :p:D

Finally, short of taking one engine and trying different throttle body configurations on it I don't think we'll ever know the true answer.  I have a feeling this may have been done in an old edition of CCC but wouldn't like to say for sure.

Posted

The comparison was between DCOE type, and roller barrel type, IIRC. As you say, the differences were small enough as to make the roller barrels not worth the extra expense, at the time............

Posted
As you say, the differences were small enough as to make the roller barrels not worth the extra expense, at the time............

Ooooh, I never said that - stop putting words in my mouth !!  :p  :D  :D

Although in the case of roller barrel throttle bodies I'm inclined to agree with that assessment.  There are some advantages at full throttle particularly, as I understand it, when using twin injector set ups when the second injector is spraying fuel into the mouth of the ram pipe.

Posted

Skim reading/too many customers...........would you like me to edit it?

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

Please review our Terms of Use, Guidelines and Privacy Policy. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.